Simulation Study On The Soil Water And Salt Movement Under The Condition Of Salt Leaching In Shule Irrigation District

With the Comprehensive Development Project of the Agricultural Irrigation and Resettlement of Shule River in Hexi Corridor, this paper analyzed the salt washing experiments of different types of saline land and constructed water and salt transport model. This construction was based on the summarize of computational theory and practice of saline land improvement, soil water and salt movement, water resources planning and management and system analysis at home and abroad, and combined with the types, distribution, regionalization of saline land, current situation of groundwater level distribution and irrigation in Hexi irrigation district. According to large-quota vertical irrigation and horizontal gutter drainage experiment, water and salt transport was simulated in using HYDRUS Software. By doing this, efficiency of salt washing under different salt content, different irrigation water content and influence of washing for water and salt in field were analyzied. Then the time variation process of water and salt was predicted and reasonable salt washing system was proposed.(1)Water and salt transport model was constructed. One-dimensional water and salt dynamic model was constructed and the parameters and boundary conditions were determined by analysising water and salt transport process under washing improvement. The model was solved by finite difference method.(2)With the date of large quota vertical irrigation experiment, water and salt transport simulation was carried out. The model's validation was conformed in contrast to the results of experiments. The simulation results basically correspond with measured data.(3)Simulation study on one dimensional soil water-salt transport regulation was carried out. The results showed that: salt gradually transported into lower layer and salt content of cultivated horizon was significantly reduced in large-quota vertical irrigation experiment. The larger the water content was, the more the leaching of salt was. The larger the initial salt content was, the smaller the cumulative infiltration was and the longer the infiltration time was. Simulation period was divided basing on cumulative infiltration.(4)Salt washing system for large-quota vertical irrigation improvement was made. Continuous irrigation was superior to the time interval irrigation of which the time was too long. The washing effect wasn't distinct for three-time and four-time irrigation mode with same irrigation quota and same average water content. The best effect of desalination was irrigating with a less quota of water as first irrigation content and then with two large quota. The more the irrigation water was, the better effect of desalination was, but excess water had no contribution for desalination. In terms of the above mentioned factors, salt washing system was established.(5)Simulation study on salt washing system of horizontal gutter drainage was performed in using typical profile. Salt washing system was established according to different salt content.